New EPA regulations on lead paint in homes -- first promulgated in April 2008 and just made effective -- apply to all homes, child care facilities, and schools built before 1978 unless testing establishes that the structure is free of lead paint.

According to the best estimates I can find, there are 72 to 80 million children aged 18 and under in the United States. Children under 6 are most vulnerable to the consequences of lead poisoning, defined as lead levels greater than 10 micrograms of lead per deciliter of blood, “the level at which CDC recommends public health actions be initiated.”

According to the CDC, the greatest source of the elevated lead levels is lead-based paint and lead contaminated dust. The problem was recognized in 1978, when the use of lead in paints was banned for housing use in the U.S. The CDC contends: “All houses built before 1978 are likely to contain some lead-based paint.” The CDC estimates that paint has deteriorated in 24 million U.S housing units, of which 4 million “are homes to one or more young children.”

Yet the National Association of Home Builders (NAHB) claims: “Only 24 percent of homes built between 1961 and 1978 used lead paint.”

The EPA reports that the new regulations affect about 38 million homes and apartments, or 40 percent of the existing housing stock in the country. But NAHB Environmental Communications Director Calli Schmidt, in private correspondence with me, said the EPA’s lower total cost figures are based on the existence of an opt-out provision, which the EPA is removing. As the health consequences of lead toxicity are most serious with pregnant women and children under 6, the original draft regulations allowed a provision for homeowners who had no such residents living in their dwellings.

Indeed, according to Schmidt, the new regulations will cover “all 79 million homes built before 1978.”

If that is the case, about 80 percent of U.S. housing stock will be affected.